Hiding in the THz is the easiest; paint it black and fly at night. Lower THz, e.g. IR, is attenuated by the atmosphere. Useful but limited, and stealth planes

Hiding in the THz is the easiest; paint it black and fly at night. Lower THz, e.g. IR, is attenuated by the atmosphere. Useful but limited, and stealth planes are designed to make it harder (e.g. by mixing hot exhaust with cooler air above the wing, where the hot engine cannot easily be seen from the ground.)